i got it.
the config files are all like the perfect debian sarge page 4 says.
BUT i am using etch!
in etch (maybe in sarge - don't know) there is something different!
i created the dir with:
mkdir -p /var/spool/postfix/var/run/saslauthd
and then i have to edit /etc/default/saslauthd. i have to remove # in front od start=yes to start the daemon.
BUT THEN i DON'T have to add
instead i have to change the line
PARAMS="-m /var/spool/postfix/var/run/saslauthd -r"
OPTIONS="-c -m /var/spool/postfix/var/run/saslauthd"
editing of the file /etc/init.d/saslauthd is also not neccessary! i don't have to change the PIDFILE!
the following steps are like the tutorial says.
after starting the saslauthd have a look at /var/spool/postfix/var/run/saslauthd
if everything is ok, there must be some files in it (created by the deamon while starting). If you can't find these files there is something wrong with your rundir (with the OPTIONS=...)
hope, this helps other!